<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
          var arr = {
            A:[{city:"武汉"},{city:"广州"}],
            B:[{city:"深圳"},{city:"广州"}],
            C:[{city:"上海"},{city:"武汉"}]
        }
        // var values = Object.values(arr)
        // var res = []        
        // values.forEach(item => {
        //     item.forEach(k=>{
        //         if(!res.includes(k.city)){
        //             res.push(k.city)
        //         }
        //     })
        // });
        var list = [];
        for(var k in arr){
            list.push(...arr[k])
        }
        var res = []
        list.forEach(item=>{
            if(!res.includes(item.city)){
                res.push(item.city)
            }
        })
        console.log(res)
    </script>
</body>
</html>